The Saint-Chamond, named after the commune of Saint-Chamond, was the second French heavy tank of the First World War, with 400 manufactured from April 1917 to July 1918. Although not a tank by the present-day definition, it is generally accepted and described as such in accounts of early tank development. Born of the commercial rivalry existing with the makers of the Schneider CA1 tank, the Saint-Chamond was an underpowered and fundamentally inadequate design. Its principal weakness was the Holt "caterpillar" tracks. They were much too short in relation to the vehicle's length and heavy weight (23 tons). Later models attempted to rectify some of the tank's original flaws by installing wider and stronger track shoes, thicker frontal armour and the more effective 75mm Mle 1897 field gun. Altogether 400 Saint-Chamond tanks were built including 48 unarmed caisson tanks. The Saint-Chamond tanks remained engaged in various actions until October 1918, belatedly becoming more effective since combat had moved out of the trenches and onto open ground. Eventually the Saint-Chamond tanks were scheduled to be entirely replaced by imported British heavy tanks.

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In January 1915, the French arms manufacturer Schneider sent out its chief designer, Eugène Brillié, to investigate tracked tractors from the American Holt Company, at that time participating in a test programme in England. The original French project was to provide mobility to mechanical wire-cutting machines of the Breton-Pretot type. On his return Brillié, who had earlier been involved in designing armoured cars for Spain, convinced the company management to initiate studies on the development of a Tracteur blindé et armé ("armoured and armed tractor"), based on the Baby Holt chassis, two of which were ordered.

Experiments on the Holt caterpillar tracks started in May 1915 at the Schneider plant with a 75 hp wheel-steered model and the 45 hp all-caterpillar Baby Holt, showing the superiority of the latter.[1] On 16 June, new experiments followed in front of the President of the French Republic, and on 10 September for Commander Ferrus, an officer who had been involved in the study (and ultimate abandonment) of the Levavasseur tank project in 1908.[2]

In early 1916, the first prototype of the Schneider tank was assembled in an army workshop. It featured tracks from the American-made Holt caterpillar tractors that were already used in France for towing heavy artillery. Private Pierre Lescure designed the fighting compartment. Lieutenant Fouché lengthened the tracks to improve trench-crossing ability. In this early form the prototype of the Schneider was called Tracteur A - not for security reasons, but because nobody knew exactly how to call such vehicles; the French word char was not yet applied to tanks. Eugène Brillié, the chief designer at Schneider, rejected this Tracteur A prototype. Instead he had invented a tail for his own tank's chassis thus providing the same trench crossing ability but for less overall weight and length.

While Brillié began to assemble this second prototype which was to become the Schneider CA1, the arms manufacturer Forges et Aciéries de la Marine et d'Homécourt (aka "FAMH"), based at Saint-Chamond, Loire, was given an order for 400 tanks by the French government, a political move prompted by General Mourret of the Army "Service Automobile". Saint-Chamond intended to build a tank that would be partly similar to the Schneider. Brillié refused to share his patents for free, and Saint-Chamond refused to pay. As a result the "Forges et Acieries de la Marine et d'Homecourt" company, being unable to replicate certain patented details (notably the tail) of the new Schneider tank, developed its own proprietary design: the "Char Saint-Chamond". It included a "Crochat-Colardeau" gasoline-electric transmission, a traction system already used on railcars in service with the French railways. Furthermore, the freedom to design a heavier and larger tracked vehicle gave Saint-Chamond the opportunity to upstage the Schneider company. This they did by installing on their "Char Saint-Chamond" a more powerful, full size 75 mm field gun plus 4 Hotchkiss machine guns instead of the two machine guns present on the Schneider tank.

The Char Saint-Chamond on display at the Musée des Blindés in Saumur, the last surviving example.

Saint-Chamond's technical director was Colonel Émile Rimailho, an artillery officer who had become dissatisfied over the insufficient reward he had received for helping design the famous Canon de 75 modele 1897 field gun as well as the Modele 1904 155 mm "Rimailho" howitzer. Following his departure from the French State arsenal system (APX) and joining Saint-Chamond, Rimailho designed a 75 mm field gun similar to the Mle 1897 75 mm gun he had co-developed with Sainte-Claire Deville. It was the proprietary Canon de 75mm TR Saint-Chamond (Modele 1915), designed to fire the regular French 75 mm ammunition. Colonel Rimailho, who had a direct financial interest in selling his company's gun, induced the Ministry of War to specify that the new Saint-Chamond tank would also mount the Saint-Chamond made 75. In so doing Rimailho had also upstaged the Schneider CA1 tank which could only be fitted with a smaller Schneider-made fortress gun firing a 75 mm reduced charge ammunition. To accommodate a regular length and full size 75 mm field gun, a hull longer than on the Schneider tank was essential. The earliest Saint-Chamond prototype, a tracked vehicle longer and heavier than the Schneider tank was first demonstrated to the French military in April 1916.

When Colonel Jean Baptiste Eugène Estienne, who had taken the initiative to create the French tank arm, learned that an order for 400 additional tanks had been passed on April 8, 1916, he was at first quite elated. When it later became apparent that they would be of a different type, Estienne was shocked and wrote:

I am painfully surprised that an order has been launched of this importance without asking the opinion of the only officer who, at the time, had undertaken a profound study of the technical and military aspects involved and who had brought the supreme commander to the decision to take this path [towards a tank arm].[3]

The Char Saint-Chamond showing the overhanging front hull and the later M.1897 75 mm field gun

As a result of Rimailho's manipulations, the new tank had become a rather cumbersome and underpowered vehicle. It lacked a rotating turret, instead using a large overhanging front compartment housing the long 75 mm gun protruding from the nose.

Within the forward fighting compartment and on the left was the driver, also the vehicle commander. On the right a machine gunner operated the front Hotchkiss machine gun. This machine gunner was also responsible for the breech operation of the 75 mm gun which he had to perform after pivoting on his seat to the left. A loader (referred to in some sources as the gunner) adjusted the gun's elevation, observing the target through a small hatch in the front of the tank, which left him vulnerable to enemy fire. Traversing the 75 mm gun required traversing the whole tank, and this was performed by the driver. A second fighting compartment at the back held one machine gunner next to the secondary driver's position, where the tank could also be driven backwards by the mechanic in an emergency. Between those two compartments stood in the open the gasoline engine and the electric generator. Narrow passageways on both sides of the engine connected the front and rear compartments. The passageways also held Hotchkiss positions, one on each side in front of the engine. Altogether, the Saint-Chamond had four Hotchkiss M1914 machine gun positions: one in the front, one in the back and one on each side of the tank.

Despite weighing 23 tons, the tank could manage a top speed of 12 km/h. This speed was seldom achieved in the field as the long nose was prone to digging into the ground. The relatively high maximum speed on flat ground was made possible by the "Crochat Colardeau" transmission which coupled a Panhard-Levassor 4 cylinders 90HP sleeve-valve gasoline engine to an electric generator capable of giving an output of 260 amperes under 200 volts. The generator was connected to two separate electric motors, one for each track, thus permitting perfect gradual steering of the tank.

Due to its short tracks and over-extended body, the vehicle experienced major difficulties in crossing trenches and overcoming obstacles. This led to such negative reactions by the crews in training that a special mention was passed on to General Headquarters:

Nobody wants to serve on the Saint-Chamond. Second Lieutenant de Gouyon, principal Saint-Chamond driving instructor at Marly, has publicly declared that it has become virtually impossible for him to continue to carry on and, since he is a Member of Parliament, that he will request to have the whole matter placed on the next parliamentary agenda.[4]

Originally the crew of nine men was protected by 11 mm of steel armour on the sloping front and 17 mm on the sides. Later on, the addition of an extra layer of spaced 8.5 mm armour on the front improved protection. Beginning with the 151st vehicle, the roof was also redesigned with a double slope so that satchel charges and grenades would slide off. Concurrently, the original two observation turrets in front and on top were done away with and replaced by a single low profile square turret permitting front and sides vision by the tank's driver/commander. With time, the tracks were also widened in two steps from 324 mm to 412 mm to lower their ground pressure. After Saint-Chamond tank No 210 the more effective Model 1897 field gun was installed instead of Rimailho's (profitable) 75 mm Saint-Chamond gun. At about the same time barrel-like rollers were added underneath the front and rear of the tank to help crossing trenches. This improved version was later called, unofficially, the Modèle 18. Production slowed down in March 1918, after at least 377 had been assembled, and ceased completely in July 1918.

Initially, forty eight Saint-Chamond tanks were modified as supply and recovery vehicles that could tow the lighter Schneider tanks. Their first action as a fighting vehicle took place at Laffaux Mill on May 5, 1917. Sixteen Saint-Chamond tanks were engaged there, several of them getting stuck into some trenches, but only three were destroyed in combat. During the rest of the war, twelve groups in total were formed with Saint-Chamond tanks : Artillerie Spéciale Nos. 31–42. In mid-1918, since combat had left the trenches for the open fields, it was used to engage German field gun batteries (Nahkampfbatterien) at a distance with its 75 mm cannon. The Saint-Chamond proved at last quite effective in this specialist assault gun role. The Saint-Chamond's final engagement in battle, with initially 16 tanks, took place in early October 1918, in support of the U.S. First Division near Montfaucon. As reported in Ralph Jones et al. (1933) in reference to this last engagement : "The Saint Chamond tanks were handicapped by damage to their tracks, by derailments, by the breakage of the caps of connecting rods on forward bogies and of track pins". By that time, the Renault FT tank had taken over the major role in the French tank force and had also been purchased by the American Expeditionary Forces in France.

After the war 54 were rebuilt as ammunition carriers; the remainder were scrapped. There are unsubstantiated stories about Poland using the tank against the Red Army in 1920. If true these specimens were in all probability not from the Soviet Army—the latter never had been supplied with them and the French Expeditionary Forces to Russia were only equipped with the Renault FT.

The last Saint-Chamond tank remaining in existence (an improved mid-1918 model), alongside other French tanks of World War I (Schneider CA1 and Renault FT), is preserved at the Musée des Blindés at Saumur, France. It had survived, together with a Schneider CA1 tank of the same vintage, at the Aberdeen Proving Grounds Ordnance Museum in Maryland and was later donated by the U.S. to the French government. Between 2015 and 2017 it was restored to running condition and repainted in a World War I camouflage scheme, at a cost of €120,000. It will take part in various displays throughout 2017 to mark the centenary of the first use of tanks by the French army.[5]